John Varley, 61, a director of mining giant Rio Tinto, has been charged with conspiracy to commit fraud by the UK Serious Fraud Office.

He has been charged with two counts of conspiracy to commit fraud by false representation, and one count of providing unlawful financial assistance.

Mr Varley is the former chief executive officer of Barclays.

John Varley, a director of mining giant Rio Tinto, has been charged with conspiracy to commit fraud by the UK Serious Fraud Office. Photo: Daniel Munoz

The charges come after an investigation by the Serious Fraud Office, which was first announced in August 2012.

The charges were revealed in a statement released by the Serious Fraud Office on Tuesday.

The statement said: "The charges relate to Barclays Plc's capital raising arrangements with Qatar Holding LLC and Challenger Universal Ltd, which took place in June and October 2008, and a US$3billion loan facility made available to the State of Qatar acting through the Ministry of Economy and Finance in November 2008."

The statement also revealed that Barclays was charged with two counts of conspiracy to commit fraud by false representation, and one count of providing unlawful financial assistance.

And it said three other people had been charged with conspiracy to commit fraud by the Serious Fraud Office, naming them as Roger Alan Jenkins, 61, of California, Thomas Llewellyn Kalaris, 61, of London, and Richard William Boath, 58, of London.

A spokesman for Rio Tinto declined to comment on the matter when contacted on Tuesday evening.

Rio Tinto is one of Australia's biggest publicly listed companies, and one of the world's biggest miners.

The defendants will appear before Westminster Magistrates' Court on July 3, 2017.